The Sentinels, those mutant-hunting robots, are a staple of X-Men stories going all the way back to 1965. They have evolved dramatically over the years as artists and writers refine and re-evaluate their conception of the ‘bots, and how they relate to other characters. They take a pretty huge leap forward in X-Men: Days of Future Past, both visually, and in terms of their capabilities. There’s a certain visual relationship to the old X-Men character Nimrod, and also to another character, with the reasons for that latter one made explicit in the film. Below, we have a collection of Sentinel concept art develop from Days of Future Past, showing some of the page to screen evolution.

What we see on screen in scenes set in the 2020s isn’t much like the famous Sentinel designs seen in comics pages from the original Days of Future Past story, but the ’70s designs are familiar in some ways. The “future” Sentinels, meanwhile, ended up having a big design element taken from Mystique. Not only do the robots feature her DNA, but their shifting armor spines resemble Mystique’s own skin.

These concept shots, created and posted by Framestore, show both ends of the design spectrum. What’s interesting about many of these shots is that there is a distinct feminine aspect to some of the physical designs. Had that gone forward even more for the final concept, there would have been one more element of Mystique in the mix. (As is, the future Sentinels are far more lithe and almost even sensuous than the blocky original comic book designs.)